Functional Software descriptionDCS 500 Software Description 31Window ControlPrincipleTIMETORQ REF+SPC OUTPUTSPEED ACTSPC OUTPUTWIN SIZE (2004)SPEED ERROR > WIN SIZE / 2SPEED ERROR < WIN SIZE / 2SPEED ERROR = 0Figure 16 Window control functionThe idea of Window control is to deactivate the speed control aslong as the speed deviation remains within the set window. Thisallows the external torque reference to affect the process directly.Application ex-ample for Win-dow ControlIn master/follower drives, where the follower section is torque con-trolled, the window control is used to keep the speed deviation ofthe section under control. The speed error output to the speedcontroller is zero when speed error is less than WINSIZE/2.If the load of the follower disappears because of a disturbance inthe process, the speed error will be outside the window. The speedcontroller works and its output OUT (12004) is added to the torquereference [TREF SPC] (2407).Speed control brings the speed difference back to the window. Thisfunction could be called overspeed or underspeed protection in thetorque control mode.Enabling theWindow ControlThe window control is activated by setting the input [WIN MODE](2003) to logical state 1.The parameter TREF SEL (2406) in the TORQ REF HANDLINGfunction block must be set to value 5 when window control is used.Determining theWindow SizeThe size of window determined by parameter WIN SIZE (2004),scaling is the same as for the speed reference. See the previousfigure "Window control function".Output connec-tion pointsOutput OUT(12001) is normally connected to [IN] (2006) input inthe SPEED CONTROL function block.
